Gas tank holder



FIG. 1 is a top and side perspective view of a gas tank holder showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a side elevational view thereof; and,

FIG. 5 is an opposite side elevational view thereof. 

The ornamental design for a gas tank holder, as shown and described. 